Liquid tank leakage detection system

Abstract

A liquid tank leakage detection system includes a standpipe and associated measuring pipe together with a sealing connection to the filler pipe of a liquid tank system. A liquid level detector used in cooperation with the measuring pipe includes a float coupled to a measuring beam having one end fixed and the other end coupled to the float. Level changes within the liquid system produce position changes of the float which in turn causes bending or flexing of the beam. A bridge detecting circuit including strain gauges coupled to the flexing beam is operative to provide an output signal indicative of the extent of liquid level changes. A thermocouple is positioned within the liquid tank to provide a temperature compensating signal for use by the measurement system.

That which is claimed is: 
     
       1. For use in detecting leakage within a liquid tank having a filler pipe, a leakage detection system comprising: a standpipe having an elongated body defining a first open end and a second closed end, a first internal passage and a spout extending therefrom;   coupling means for sealingly coupling said first internal passage to the filler pipe of the tank such that a quantity of liquid may be introduced into said standpipe filling the filler pipe, said coupling means and a portion of said standpipe to establish a liquid level therein;   a float configured to float upon the liquid;   a sensing beam having a fixed end and a free end;   beam support means coupled to said fixed end of said sensing beam holding it stationary;   temperature means for measuring the temperature of the liquid within the tank.   strain measuring means operatively coupled to said sensing beam responsive to strain or bending thereof; and   float coupling means coupling said float to said free end of said sensing beam such that movement of said float causes strain or bending of said sensing beam said float coupling means including a rigid arm having a first end fixed to said free end of said sensing beam and a second end and a float line coupling said float to said second end of said arm.   
     
     
       2. A leakage detection system as set for in claim 1 wherein said sensing beam and said arm are generally horizontal and said float line is generally vertical. 
     
     
       3. A leakage detection system as set forth in claim 1 wherein said sensing beam is generally vertical and wherein said arm is generally L-shaped having a vertical portion at said first end and a horizontal portion at said second end. 
     
     
       4. A leakage detection system as set forth in claim 1 wherein said strain measuring means include a resistive bridge circuit having: a pair of strain gauges operatively coupled to said sensing beam;   a pair of resistors coupled to said pair of strain gauges to form said resistive bridge circuit;   a power supply coupled to said resistive bridge circuit; and   circuit means, coupled to said resistive bridge circuit, responsive to unbalances therein to produce a first output signal indicative of float movement.   
     
     
       5. A leakage detection system as set forth in claim 4 wherein said temperature means produce a second output signal indicative of liquid temperature and wherein said circuit means include multiplexing means for adjusting said first output signal in response to said second output signal. 
     
     
       6. A leakage detection system as set forth in claim 5 wherein said temperature means include a temperature sensor within the tank and wherein said second output signal includes a temperature indicative signal therefrom. 
     
     
       7. For use in determining leakage within a liquid tank having a filler pipe, a leakage detection system comprising: a standpipe having an elongated body defining a first open end and a second closed end, a first internal passage and a spout extending therefrom;   a measuring pipe having a junction in communication with said first internal passage and ah open end and a second passage therebetween;   coupling means for sealingly coupling said first internal passage to the filler pipe of the tank such that a quantity of liquid may be introduced into said standpipe filling the filler pipe, said coupling means and a portion of said standpipe and said measuring pipe to establish a liquid level within said first and second passages;   a float configured to float upon the liquid within said second passage;   a sensing beam having a fixed end and a free end;   beam support means coupled to said fixed end of said sensing beam holding it stationary:   strain measuring means operatively coupled to said sensing beam responsive to strain or bending thereof; and float coupling means coupling said float to said free end of said sensing beam such that movement of said float causes strain or bending of said sensing beam.   
     
     
       8. A leakage detection system as set forth in claim 7 further including temperature means for measuring the temperature of the liquid within the tank. 
     
     
       9. A leakage detection system as set forth in claim 8 wherein said float coupling means include: a rigid arm having a first end fixed to said free end of said sensing beam and a second end; and   a float line coupling said float to said second end of said arm.   
     
     
       10. A leakage detection system as set forth in claim 9 wherein said sensing beam and said arm are generally horizontal and said float line is generally vertical. 
     
     
       11. A leakage detection system as set forth in claim 9 wherein said sensing beam is generally vertical and wherein said arm is generally L-shaped having a vertical portion at said first end and a horizontal portion at said second end. 
     
     
       12. A leakage detection system as set forth in claim 9 wherein said strain measuring means include a resistive bridge circuit having: a pair of strain gauges operatively coupled to said sensing beam;   a pair of resistors coupled to said pair of strain gauges to form said resistive bridge circuit;   a power supply coupled to said resistive bridge circuit; and   circuit means, coupled to said resistive bridge circuit, responsive to unbalances therein to produce a first output signal indicative of float movement.   
     
     
       13. A leakage detention system as set forth in claim 12 wherein said temperature means produce a second output signal indicative of liquid temperature and wherein said circuit means include multiplexing means for adjusting said first output signal in response to said second output signal.